The semiconductor industry is constantly producing smaller and more complex semiconductors, sometimes called integrated circuits or chips. This trend has brought about the need for smaller chip packages with smaller footprints, higher lead counts, and better electrical and thermal performance, while at the same time meeting accepted reliability standards.
In recent years a number of microelectronic packages have been produced to meet the need for smaller chip packaging. One such package is referred to as a chip scale package (CSP). CSPs are so called because the total package size is similar or not much larger than the size of the chip itself. Typically, the CSP size is between 1 and 1.2 times the perimeter size of the chip, or 1.5 times the area of the die. One example of a CSP is a product developed by TESSER® called “MICRO BGA” or μBGA. In a CSP, the semiconductor has a set of bond pads distributed across its surface. A first surface of an insulating, flexible film is positioned over the semiconductor surface. Interconnect circuitry is positioned within the film. Electrical connections are made between the interconnect circuitry and the semiconductor bond pads. Solder balls are subsequently attached to a second surface of the film in such a manner as to establish selective connections with the interconnect circuitry. The solder balls may then be attached to a printed circuit board.
CSPs may be used in connection with memory chips. Memory chips may be grouped to form in-line memory modules. In-line memory modules are surface mounted memory chips positioned on a circuit board.
As memory demands increase, so does the need for increased memory capacity of in-line memory modules. A need has also arisen for materials and methods that lead to increased performance by more closely matching the coefficient of thermal expansion of the materials used in these memory modules. Examples of such in-line memory modules are single in line memory modules or SIMMs and dual in-line memory modules or DIMMs. DIMMs have begun to replace SIMMs as the compact circuit boards of preference and essentially comprise a SIMM wherein memory chips are surface mounted to opposite sides of the circuit board with connectors on each side.
A problem with in-line memory modules is that adding more chips to the circuit board spreads out the placement of the chips on the circuit card and therefore requires reconfiguration of the circuit card connectors and their associated connections on the motherboard, which means replacing the memory card and in some cases the motherboard.
Another problem with current in-line memory modules is that a separate heat spreader must be positioned across a set of memory chips. The heat spreader adds cost to the assembly process and adds significant weight to the module.
Existing Multi-Chip Modules (MCM's) typically connect the transmission channel to semiconductors via electrical contact points or ball-outs on the MCM. Each electrical contact point then connects to a semiconductor in the MCM via an electrical lead, so that a signal may be transmitted along the transmission channel to each semiconductor via that semiconductor's electrical lead. However, each successive electrical lead slightly degrades the signal, by placing a load on the signal. By the time the signal reaches the last semiconductor connected to a transmission channel, the signal may have degraded so as to be unusable.
Modem MCM's, such as those disclosed in the U.S. patent application Ser. No. 09/564,064, disclose MCMs that include relatively long electrical leads. The longer the electrical lead, the more the signal degradation. This is because the speed of the signal is inversely related to the length of the electrical lead. Therefore, existing MCMs can only handle a maximum of approximately thirty two semiconductors connected to a single transmission channel before the signal has degraded to an unusable form.
In view of the foregoing it would be highly desirable to provide a semiconductor module that overcomes the short-comings of the abovementioned prior art devices.